Embodiments of the present invention relate to solid-state light devices, and more specifically to packages for solid-state light devices.
A light-emitting diode (LED) is a semiconductor device that produces light when an electric current is passed therethrough. LEDs have many advantages over conventional lighting sources, including compact size, low weight, longer life time, high vibration resistance, and higher reliability. In addition to having widespread applications for electronic products as indicator lights, LEDs also have become an important alternative light source for various applications where incandescent and fluorescent lamps have traditionally dominated, such as residential, commercial, and industrial lighting.
In a typical LED-based white light producing device, a monochromatic LED is encapsulated by a transparent material containing appropriate compensatory phosphors. The wavelength(s) of the light emitted from the compensatory phosphor is compensatory to the wavelength of the light emitted by the LED such that the wavelengths from the LED and the compensatory phosphor mix together to produce white light. For instance, a blue LED-based white light source produces white light by using a blue light LED and a phosphor that emits a yellowish light when excited by the blue light emitted from the LED. In these devices the amount of the phosphor in the transparent material is controlled such that only a fraction of the blue light is absorbed by the phosphor while the remainder passes unabsorbed. The yellowish light and the unabsorbed blue light mix to produce white light.
Another exemplary scheme uses an LED that produces light outside of the visible spectrum, such as ultraviolet (UV) light, together with a mixture of phosphors capable of producing either red, green, or blue light when excited. In this scheme, the light emitted by the LED only serves to excite the phosphors and does not contribute to the final color balance.
To provide an operational lamp, one or more LED dice are typically mounted on a substrate that provides electrical contacts and mechanical couplings and covered with one or more layers of optically transparent and/or wavelength-shifting materials, in some cases including a primary lens to direct the exiting light. This combination of LEDs, substrate, and optical materials is sometimes referred to as a “package.” The lamp itself may also include a secondary lens, heat sink, mechanical and/or electrical connections allowing the lamp to be installed in a light fixture, and so on.